This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The proposed XAS experiments are part of a project designed to examine how nature designs proteins to recognize one metal (or small group of metals) from all the metals present in cells, and generate specific biological responses. Proteins involved in nickel trafficking in E. coli and H. pylori were chosen because of the desire to examine an entire trafficking system (simplicity of the nickel traffic pattern) in order to understand the general features of specific metal recognition, and because of the potential for antibiotic strategies involving interference with bacterial nickel trafficking. XAS provides the main structural tool for examining the structure of cognate and non-cognate metal ions bound to metallotransporters, metallochaperones, and metalloregulators.